JP2007157508A - Gas liquid separator and fuel cell power generation system with gas liquid separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas liquid separator capable of surely and promptly separating and discharging only a liquid phase fluid from a gas-liquid two phase fluid, and to provide a fuel cell power generation system using it. <P>SOLUTION: The fuel cell power generation system includes a fuel cell body 1, a reactant gas supply system 2 supplying reactant gas to the fuel cell body 1, a water recovery system 3 recovering water contained in reacted gas discharged from the fuel cell body 1 and a battery body cooling system 4 removing heat generated by the battery body 1. The gas liquid separator 10 is provided in a part of piping constituting the water recovery system 3 or the fuel cell body 1. The gas liquid separator 10 has discharge piping 11 branched from a cooling water tank 11 or a heat-exchanger tank 17 and a porous body 13 provided in the discharge piping 11. The porous body 13 separates liquid and gas from the gas-liquid two phase fluid by capillary force of the liquid currently held in the pores. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas-liquid separation device using a porous capillary force and a fuel cell power generation system including such a gas-liquid separation device.

  In recent years, fuel cells have attracted attention as highly efficient energy conversion devices. In particular, solid polymer fuel cells that use proton-conducting solid polymer membranes as electrolytes have a compact structure and high power density, and can be operated with a simple system. It is attracting attention not only as a power source but also as a power source for space and mobile use.

  The outline of the prior art known as such a polymer electrolyte fuel cell power generation system will be described below with reference to FIG. This system includes a fuel cell main body 1, a reaction gas supply system 2 for supplying a reaction gas to the fuel cell main body 1, and a water recovery for recovering water contained in the existing reaction gas discharged from the fuel cell main body 1. The system 3 and the battery body cooling system 4 for removing heat generated in the battery body are configured as main modules. The main modules are described in detail below.

  The fuel cell main body 1 supplies a membrane electrode complex in which gas diffusion electrodes (fuel electrode 1a and oxidant electrode 1b) are arranged on both sides of a solid polymer membrane, and fuel gas and oxidant gas to the gas diffusion electrode, respectively. In this configuration, a plurality of unit cells each including a reaction gas supply separator provided with reaction gas supply grooves are stacked through a cooling plate 1c that removes heat generated during power generation. In addition, a reaction gas supply manifold and a reaction gas discharge manifold for supplying a reaction gas to each reaction gas supply separator or discharging a reaction gas from each reaction gas supply separator are provided on the side surface of the laminate. As the solid polymer membrane, perfluorocarbon sulfonic acid (Nafion R: DuPont, USA), which is a proton exchange membrane, is generally known. As the gas diffusion electrode, a carbon porous plate having a catalyst layer using platinum or the like as a catalyst is generally used.

  When a fuel gas containing hydrogen as a main component and an oxidant gas (air) are supplied to the fuel cell main body 1, the following electrochemical reaction proceeds in each unit cell, and about 1V is generated between the electrodes of each unit cell. An electromotive force is generated.

Fuel electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (Formula 1)
Oxidant electrode: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (Formula 2)

  At the fuel electrode, as shown in (Formula 1), the supplied hydrogen is dissociated into hydrogen ions and electrons. Hydrogen ions move through the solid polymer film, and electrons move through the external circuit to the oxidant electrode. On the other hand, at the oxidizer electrode, as shown in (Formula 2), oxygen in the supplied air reacts with the hydrogen ions and electrons to generate water. At this time, electrons passing through the external circuit become current and can supply power. Since the gas that has been supplied to the fuel cell body 1 and was not used for the reaction and the humidified water vapor and the water generated by the cell reaction are discharged from the fuel cell body 1 as the already reacted gas, a large amount of moisture is present in the already reacted gas. included.

  The reactive gas supply system 2 includes an air supply system 2a and a fuel gas supply system 2b. In a polymer electrolyte fuel cell, a solid polymer membrane as an electrolyte is proton-conductive in a wet state, so that the reaction gas supply system 2 is generally provided with a humidifier 2c. However, when a hydrocarbon such as methane is used as a raw fuel, a fuel reformer 2d and a heating burner 2e are required for reacting the fuel with water vapor to reform it into a hydrogen-rich gas. Since the reformed fuel gas contains water vapor, the fuel gas supply system 2b may not be humidified.

  In FIG. 6, the steam supply line to the fuel reformer 2d necessary for steam reforming is omitted. Further, 2f is a heat exchanger provided in the exhaust system of the burner 2e, and 2g is a supply pipe for reaction gas sent from the fuel reformer 2d and the humidifier 2c to the fuel cell main body 1.

  The moisture recovery system 3 is a system for removing moisture contained in the already-reacted gas after the cell reaction discharged from the fuel cell body 1, and is generally composed of a heat exchanger 3a and a gas-liquid separator 3b. It is. The water recovered in the gas-liquid separator 3b on the oxidizer electrode side is water that is pre-humidified in the reaction gas and water generated by the reaction of (Equation 2) in the fuel cell body 1, and generally the amount of water to be recovered Therefore, the recovered water is recovered in the cooling water tank 4a by the pump 3c and used as cooling water or humidified water. In addition, the already reacted air after moisture recovery is discharged out of the system system.

  The water recovered by the gas-liquid separator 3a on the fuel electrode side is mostly water previously humidified in the reaction gas or water contained in the fuel reforming and may be discharged outside the system. When performing a self-supporting operation (operation without supplying water to the system from the outside), it may be collected in the cooling water tank 4a by the pump 3c. When a hydrocarbon such as methane is used as a raw fuel, the remaining fuel gas after moisture recovery is supplied to the fuel reformer 2d by the remaining fuel gas recovery line 3d in order to supply heat necessary for fuel reforming. Is supplied to the burner 2e provided for combustion and burned.

  The battery main body cooling system 4 is a system for discharging reaction heat generated when power is generated by the fuel cell main body 1 to the outside of the system. The coolant stored in the coolant tank 4a by the pump 4b is circulated to the cooling plate 1c of the fuel cell main body 1 through the coolant circulation pipe 4c. The exhaust heat recovered in the cooling water tank 4a is recovered by the heat exchanger 4d and used as heat. It can be used directly as hot water. Further, when the coolant is water, a part of the coolant can be supplied to the humidifier 2c as reaction gas humidified water and used.

  In the above polymer electrolyte fuel cell power generation system, a gas containing a large amount of water vapor flows in the residual fuel gas recovery line 3d for supplying the residual fuel gas after gas-liquid separation to the combustion burner 2e for the fuel reformer. For this reason, when the temperature of the pipe is lowered even partly, the water vapor condenses in that part and becomes a gas-liquid two-phase fluid, causing various problems. For example, if water vapor condenses in the residual fuel gas recovery line 3d that supplies the residual fuel gas after gas-liquid separation to the fuel reformer combustion burner 2e, the fuel reformer combustion burner 2e may misfire.

  Further, the coolant held in the coolant tank 4a of the battery main body cooling system 4 is a gas-liquid two-phase fluid containing minute bubbles. This is because during the operation of the system, the coolant is at a temperature of about 60 ° C. to 80 ° C. due to exhaust heat. This is to involve them. As described above, when a gas phase is mixed in the cooling liquid, cavitation occurs in the water pump 3c, and the water supply capability is remarkably lowered, resulting in unstable cooling performance. Conventionally, measures have been taken such as providing an air vent container upstream of the water pump 3c, but sufficient effects have not been obtained.

  As countermeasures, Patent Document 1 discloses a method of keeping gas piping warm in order to prevent condensation of water vapor, and Patent Document 2 discloses a method of providing a water absorber filled with a water absorbing agent as means for removing water. Patent Document 3 discloses a method for gas-liquid separation using water vapor in a reaction gas as condensed water. However, these methods are not preferable because of their complicated structure or insufficient gas-liquid separation function.

  In order to solve the problems caused by the gas-liquid two-phase fluid in such a fuel cell power generation system, it is conceivable to provide gas-liquid separators at various points in the system. For example, in Patent Document 4, a liquid discharge pipe is branched in the middle of a pipe through which a gas-liquid two-phase fluid flows, and a porous body is disposed at the branch portion, so that the liquid is discharged through the porous body. A gas-liquid separation device is shown in which the gas flows to the piping side, and the gas is blocked by the capillary force of the liquid that has entered the pores of the porous body and does not flow out to the discharge piping side.

  Certainly, the gas-liquid separation device of Patent Document 4 has an advantage that gas-liquid can be effectively separated with a simple configuration in which a porous body using capillary force is provided at a branching portion of a pipe. However, this type of gas-liquid separation device cannot be used in various parts of the fuel cell power generation system as described above, because the gas blocking effect is lost if no liquid is always present in the porous body. That is, the gas flowing in the fuel cell power generation system is not always a gas-liquid two-phase body throughout its operation.

  Therefore, even if there is a gas sealing effect in a state where the liquid is trapped in the porous body, the liquid present in the porous body is evaporated and removed while the gas flows in the pipe, and the wet due to capillary force Since the sealing function is lost, there arises a problem that gas leaks from the portion to the branch pipe side. In addition, when power generation is stopped, gas does not circulate in the piping or purge gas with low humidity circulates, so that the liquid present in the porous body is evaporated and removed, and the wet seal function due to capillary force is lost. Therefore, there arises a problem that the reaction gas leaks at the time of startup.

JP 2000-12057 A JP 2002-100385 A JP 2000-357529 A JP-A-5-137933

  As described above, in the polymer electrolyte fuel cell power generation system, there is a place where a gas-liquid two-phase fluid composed of a gas phase fluid and a liquid phase fluid circulates inside, such as a reaction gas pipe and a cooling water tank. In many cases, the gas-liquid two-phase fluid in the system makes the battery performance unstable or significantly deteriorates. Therefore, it is necessary to quickly separate and discharge the liquid-phase fluid from the gas-liquid two-phase fluid.

  In order to meet these requirements, when a gas-liquid separator having a simple structure using capillary force as described in Patent Document 4 is used in a fuel cell power generation system, a gas having a relative humidity of 100% or less flowing in the pipe is used. If the liquid trapped in the porous material is lost, the sealing function due to the capillary force is lost and gas leakage occurs.

  The present invention provides a gas-liquid separator capable of reliably and quickly separating and discharging only a liquid phase fluid from a gas-liquid two-phase fluid without requiring special control such as valve operation, and a fuel cell power generation system using the same. The purpose is to do.

  More specifically, for the water recovery system, no special control such as valve operation is required, and only the liquid phase fluid is removed from the gas-liquid two-phase fluid circulating in the existing reaction gas piping without leaking the gas phase fluid. We propose a technology that can reliably and promptly separate and discharge. Regarding the battery main body cooling system, a technique is proposed in which a liquid phase fluid can be promptly separated and supplied from a cooling liquid containing minute bubbles in a cooling water tank without requiring an air vent container upstream of the water pump.

  In addition, as a gas-liquid separator used in each system of the fuel cell power generation system, a liquid that exists in a porous body can be obtained even if no liquid is supplied from a fluid flowing in a pipe such as a gas having a relative humidity of 100% or less. We propose a technology that can reliably prevent the leakage of gas flowing in the piping without causing the air to dry and the sealing function by capillary force to be exerted reliably.

  In order to achieve the above object, a gas-liquid separation device according to the present invention includes a tank for storing liquid condensed from a gas-liquid two-phase fluid, and a liquid provided at a position lower than the liquid storage surface in the tank. And a porous body that prevents the flow of gas by a capillary force provided in the discharge pipe. The average pore radius of the porous body is preferably 20 μm or less. A heat exchange means for condensing the gas phase fluid into a liquid phase fluid may be provided in the tank.

  The fuel cell power generation system of the present invention includes a fuel cell main body, a reaction gas supply system for supplying a reaction gas to the fuel cell main body, and a water for recovering water contained in the existing reaction gas discharged from the fuel cell main body. In a fuel cell power generation system including a recovery system and a battery main body cooling system for removing heat generated in the battery main body, the water recovery system includes a heat exchanger supplied with a reaction gas, and the heat A tank for storing water contained in the already-reacted gas condensed by the exchanger, a liquid discharge pipe provided at a position lower than the liquid storage surface in the tank, and a capillary force disposed in the discharge pipe Is provided with a porous body that prevents the flow of gas.

  The battery main body cooling system includes a cooling water tank that stores cooling water that circulates to cool the fuel cell main body, and discharge of liquid provided at a position lower than the liquid storage surface in the cooling water tank. A pipe and a porous body that is disposed in the discharge pipe portion and that prevents the flow of gas by a capillary force are provided.

  According to the fuel cell power generation system of the present invention having the above-described configuration, the liquid can be easily and surely removed from the gas-liquid two-phase fluid flowing through the water recovery system or the cooling system of the fuel cell body. Battery performance can be ensured. Further, as the gas-liquid separation device, a liquid discharge pipe provided at a position lower than the liquid storage surface in the tank and a porous body disposed in the discharge pipe portion are used. Since it is held in the liquid, the sealing function by the capillary force can be surely exhibited, and there is no possibility that the gas leaks through the liquid discharge pipe.

  Hereinafter, some of the best modes for carrying out the present invention will be sequentially described. In addition, the same code | symbol is attached | subjected about the part which is common in the conventional fuel cell power generation system shown in the said FIG. 6, and description is abbreviate | omitted.

(1) 1st Embodiment This embodiment arrange | positions the gas-liquid separation apparatus 10 of this invention in the cooling water tank 4a in the battery main body cooling system 4 in a fuel cell power generation system. That is, as shown in the enlarged view of FIG. 2, the drainage pipe 11 connected to the cooling water circulation pipe is connected to the bottom of the cooling water tank 4a in which the cooling water that is a gas-liquid two-phase fluid is stored. In this case, a constant amount of cooling water is always stored in the cooling water tank 4 a so that the liquid level is always higher than the connection position of the drain pipe 11. That is, the connection position of the drainage pipe 11 is determined so that the cooling water in the cooling water tank 4 a is reduced and the air above it does not enter the drainage pipe 11.

  The vent pipe 12 is branched from the drain pipe 11 provided as described above, and this is connected to the upper part of the cooling water tank 4a (above the water level of the stored cooling water). In addition, a porous body 13 having a thickness of 5 mm and an average pore radius of 15 μm was disposed on the downstream side (the side opposite to the cooling water tank 4a) of the vent pipe 12 in the drain pipe 11. The porous body 13 used in the present embodiment is a foam metal, but may be any material having corrosion resistance such as a carbon material or a resin. Further, a porous membrane such as filter paper may be used.

  In the present embodiment having such a configuration, the cooling liquid held in the cooling water tank 4a is a gas-liquid two-phase fluid containing minute bubbles for the reason described in the above-described prior art. This gas-liquid two-phase fluid is sucked into the drainage pipe 11 from the bottom of the cooling water tank by the cooling liquid circulation pump 4 b along with the operation of the fuel cell and reaches the porous body 13. Since the porous body 13 is disposed in the water in the drain pipe 11, its wet seal function is exhibited, only the liquid in the gas-liquid two-phase fluid is allowed to pass, and the gas phase fluid is the cooling water circulation pipe. It cannot move to the 4d side. As a result, the gas is trapped on the cooling water tank 4a side of the porous body 13, and the collected gas returns from the vent pipe 12 to the upper part of the cooling water tank 4a.

Generally, the wet seal function of the porous body 13 is determined by the capillary force of water in the porous body 13, and the capillary force ΔP of the porous body 13 can be calculated by the following equation.
ΔP = 2σCOSθ / r
σ: Surface tension of water θ: Contact angle of water r: Pore radius

  For example, the capillary force ΔP of the porous body 13 containing water and having a pore radius of 20 μm is about 5 kPa from the above formula. In this case, a pressure of 5 kPa or more is required to pass the gas phase fluid through the porous body 13. When the fuel cell main body 1 generates power in an atmospheric pressure atmosphere, the reaction gas supply pressure is about 3 kPa, and a wet seal function of 5 kPa or more is necessary. Therefore, the pore radius of the porous body 13 should be 20 μm or less. Is preferred.

  As described above, according to the present embodiment, air bubbles contained in the cooling water are eliminated by a simple configuration in which the porous body 13 is disposed in the drain pipe 11 provided at the bottom of the cooling water tank 4a. Only the cooling water can be circulated through the circulation pump 4d and the cooling plate 1c. As a result, the cooling efficiency of the fuel cell body and the operating efficiency of the circulation pump 4d are improved. Moreover, since the position of the drainage pipe 11 connected to the cooling water tank 4a is set to a position where the cooling water always fills the pipe, liquid always exists in the pores of the porous body 13 and the capillary force is lost. Since the wet seal function is maintained, the gas in the drain pipe 11 does not leak to the cooling water circulation pipe 4d side.

  In addition, the structure of the gas-liquid separation apparatus 10 provided in this embodiment is not limited to the thing of FIG. For example, as shown in FIG. 3, by providing the porous body 13 at the inlet portion of the drain pipe 11, the gas separated by the porous body 13 can be supplied to the upper part of the cooling water tank 4a without providing the vent pipe 12. It is also possible to collect them.

(2) Second Embodiment FIG. 4 shows a second embodiment of the present invention. This embodiment is a fuel electrode side and an oxidant electrode side in the conventional fuel cell power generation system shown in FIG. The separated and discharged water is stored in the gas-liquid separators 3b and 3b, respectively, and when the amount of water reaches a certain level, the pump 3c and the valve 3e are operated to discharge the water to the cooling water tank 4a. The liquid separator 3b, the pump 3c, the valve 3e and the like are not required, and the separated and discharged water is directly discharged to the cooling water tank 4a.

  That is, in this embodiment, as shown in the enlarged view of FIG. 5, the drain pipe 11 is connected to the bottom of the tank 17 of the heat exchanger provided on the pipe of the already reacted gas from the fuel electrode 1a. The outlet of the pipe 11 is connected to the side surface of the tank 18 of the heat exchanger provided on the pipe of the already reacted gas from the oxidant electrode 1b. Further, a drain pipe 19 provided at the bottom of the tank 18 of the heat exchanger is connected to the cooling water tank 4a. In this case, the drain pipe 11 is connected to a position that is always lower than the level of the condensed water stored in the heat exchanger tank 18. In order to make the liquid level of the condensed water always higher than the connection position of the drain pipe 11, the connection position of the drain pipe 19 is always higher than the connection position of the drain pipe 11.

  In the present embodiment having such a configuration, moisture in the already reacted gas from the fuel electrode 1a condensed in the heat exchanger tank 17 passes through the gas-liquid separator 10 at the bottom of the heat exchanger tank 17 and is oxidized. The existing reaction gas from the agent electrode 1b is collected in the heat exchanger tank 18 into which it is introduced. In this case, the porous fuel 13 of the gas-liquid separator 10 reliably prevents the residual fuel gas from the fuel electrode 1a from leaking to the heat exchanger tank 18 side. On the other hand, the already-reacted gas from the oxidant electrode 1 b is condensed by the liquid (water) contained in the heat exchanger in the heat exchanger tank 18 and collected at the bottom of the heat exchanger tank 18. In this way, the liquid removed from the already-reacted gas of both systems collected at the bottom of the heat exchanger tank 18 is collected in the coolant tank 4a via the drain pipe 19.

  In this case, in this embodiment, the gas-liquid separator 10 can be provided on the drain pipe 19 of the heat exchanger tank 18, but the liquid contained in the already-reacted gas from the oxidizer electrode 1b is mainly water. In addition, since the gas from which moisture has been removed is exhausted to the atmosphere, the degree of moisture removal is gentle compared to the case of the already reacted gas from the fuel electrode 1a. The separation device 10 may not be provided.

  As described above, according to the present embodiment, the liquid phase from the gas-liquid two-phase fluid that circulates in the existing reaction gas pipe without leaking the gas-phase fluid without requiring special control such as a water pump or valve operation. Since the fluid alone is reliably and promptly separated and discharged, stable system operation is possible. That is, the gas-liquid two-phase fluid flowing in the already-reacted gas discharge pipe 2 h is condensed by the heat exchanger 16 and dropped into the tank 17. The liquid stored in the tank 17 passes through the drain pipe 11 having the porous body 13 and is discharged to the outside of the gas-liquid separator 10. On the other hand, the gas from which the liquid has been removed is sent to the reformer burner 2 e as a residual fuel gas. Sent. Further, the already reacted gas on the oxidizer electrode 1b side after the water is separated and discharged is directly discharged to the atmosphere.

  According to the present embodiment having such a configuration, the conventional gas-liquid separator, pump, valve, and the like are not required, and therefore, in the already-reacted gas from the fuel cell main body, the configuration is simple compared with the prior art. It is possible to remove the water and supply it to the atmosphere or to the combustion burner. In particular, by providing the heat exchanger 16, there is also an advantage that the liquid contained in the gas-liquid two-phase fluid is promoted to be separated and the liquid can be separated more efficiently.

The piping diagram which shows 1st Embodiment of the fuel cell power generation system of this invention. Sectional drawing which shows an example of the gas-liquid separator used for 1st Embodiment of this invention. Sectional drawing which shows the other example of the gas-liquid separation apparatus used for 1st Embodiment of this invention. The piping diagram which shows 2nd Embodiment of the fuel cell power generation system of this invention. Sectional drawing which shows an example of the gas-liquid separation apparatus used for 2nd Embodiment of this invention. The piping diagram which shows the conventional fuel cell power generation system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body 2 ... Reaction gas supply system 3 ... Water | moisture-content recovery system 4 ... Battery main body cooling system 10 ... Gas-liquid separator 11 ... Exhaust pipe 12 ... Venting pipe 13 ... Porous body 16 ... Heat exchanger 17,18 ... Heat exchanger tank 19 ... Drain piping

Claims (6)

In a gas-liquid separator that separates a liquid-phase fluid from a gas-liquid two-phase fluid composed of a gas-phase fluid and a liquid-phase fluid,
A tank for storing the liquid condensed from the gas-liquid two-phase fluid, a liquid discharge pipe provided at a position lower than the storage surface of the liquid in the tank, and a gas flow by the capillary force provided in the discharge pipe A gas-liquid separation device comprising: a porous body that inhibits water.   The gas-liquid separator according to claim 1, wherein the porous body has an average pore radius of 20 µm or less.   2. The gas-liquid separation device according to claim 1, wherein heat exchange means for condensing the gas phase fluid into a liquid phase fluid is provided inside the tank. Generated in the fuel cell main body, a reactive gas supply system for supplying reactive gas to the fuel cell main body, a moisture recovery system for recovering moisture contained in the reactive gas discharged from the fuel cell main body, and the battery main body In a fuel cell power generation system having a battery main body cooling system for removing heat to
The water recovery system includes a heat exchanger to which the already-reacted gas is supplied, a tank for storing moisture contained in the already-reacted gas condensed by the heat exchanger, and a storage surface for the liquid in the tank. A fuel cell power generation system comprising: a liquid discharge pipe provided at a low position; and a porous body disposed in the discharge pipe to prevent gas flow by a capillary force.   The heat exchanger is provided between a pre-reacted gas pipe from the fuel electrode of the fuel cell main body and a heat exchanger provided on the pre-reacted gas pipe from the oxidant electrode of the fuel cell main body. 5. The fuel cell power generation system according to claim 4, wherein the discharge pipe is connected to a cooling water tank provided in a battery main body cooling system. Generated in the fuel cell main body, a reactive gas supply system for supplying reactive gas to the fuel cell main body, a moisture recovery system for recovering moisture contained in the reactive gas discharged from the fuel cell main body, and the battery main body In a fuel cell power generation system having a battery main body cooling system for removing heat to
The battery main body cooling system includes a cooling water tank that stores cooling water that circulates to cool the fuel cell main body, and a liquid discharge pipe that is provided at a position lower than the liquid storage surface in the cooling water tank. And a porous body that is disposed in the discharge pipe portion and prevents a gas flow by a capillary force.

Images